The present invention relates to an apparatus and a method for determining localized temperatures in the breast and for detecting and assessing changes in temperature of localized areas, which is particularly useful in screening for possible localized malignancies within the breast.
Screening for breast cancer is an important diagnostic procedure. The cure rate for breast cancer before metastases are present is quite high. Hence, early detection of malignancies using a non-damaging technique is desirable.
In the United States, x-ray mammography of the breast is a primary diagnostic procedure. Patients are reluctant to be exposed to x-rays. Physicians are reluctant to prescribe mammograms, especially for women under 40 years of age. Further, younger women often have too dense tissue which makes radiographic interpretation difficult. Another factor that enters into the decisions about using mammography is the costs of the equipment required, the facility for the equipment, the x-ray technician and the diagnostician required after the test is performed. Further, x-ray mammography often is only able to detect tumors after they have been in existence for a long time, and this can present a problem with cancer detection. For example, x-ray mammography relies for the most part on microcalcification which results when the tumor has grown enough to outstrip its blood supply and parts of the tumor die, turn necrotic and the cell walls are replaced with deposits of calcium which appear as shadows on x-rays. The tumor has likely been in existence for quite some time at this point. Also, mammography can miss at least 10 per cent of all breast cancers, particularly ductal carcinoma in situ.
Yet another technique often used is palpation, which discovers the lump of a tumor by feeling it, but often only discovers the tumor after it has grown for several years.
Several techniques involve taking temperature measurements of the breast, preferably over localized areas of the breast to locate a possible tumor inside the breast. They all rely on the natural process of angiogenesis.
Tumors naturally develop a blood supply to sustain them as they grow. In the 1960's the relationship between angiogenesis and tumor growth was recognized. Angiogenesis is a prognostic indicator for malignancies in the breast. A benign tumor or growth will not develop its own blood supply and will not experience angiogenesis, while a malignant tumor does. There is a detectable differential temperature increase in the region of the tumor, sometimes as much as more than 2.degree. F. As a result of the angiogenesis, heat from the tumor is transmitted to the skin and is measurable at the skin temperature.
When a person is thermally stressed and in particular, the body is chilled, the peripheral blood vessels, including the blood vessels in the breast, constrict, restricting blood flow, which cools the breast tissue. A tumor that has experienced angiogenesis acts as a heat sink, and reacts more slowly, if at all, to thermal stress. The slower reaction of the malignant area as compared with adjacent tissue and other tissue in the breast is an indicator that angiogenesis has occurred and helps locate an area for further examination for presence of a malignant tumor.
One technique of temperature measurement that has been used is infra-red thermography as in a GST test system formerly used. It is effective to detect both benign and malignant tumors that are quite small. An infra-red probe is used to measure the breast temperature. If any area measured has an elevated temperature, the patient's body temperature is chilled to cause vasoconstriction. Temperature measurements are again recorded and compared. Because of angiogenesis, the malignant tissue will not change temperature in the same manner due to the thermal stress, that is, its temperature will only drop a small amount, if at all, as compared with the temperature of normal tissue or the temperature of a benign growth.
A GST test was not accurate enough because of the infra-red probe used and the manner in which the test was administered, so that it had too wide a temperature excursion factor. The device for performing it was too expensive and the analysis process too expensive.
Use of thermographic analysis for locating breast cancer is disclosed, for example in U.S. Pat. Nos. 3,970,074 and 4,445,516.
It has also been proposed to produce an image of breast surface temperature by the use of contacting liquid crystals which provide an image. But the image they supply is very rough or of poor quality. The accuracy of breast temperature measurements by the two known temperature sensing techniques described is not accurate to a precise range. The images obtained by these test procedures are poor in quality generally.
The GST scan, a liquid crystal technique and other temperature sensing techniques, as well as the present invention, rely upon the natural process of angiogenesis.
U.S. Pat. No. 3,970,074 describes an array of thermistors mounted on a resilient sponge that is pressed against the body, whereby the use of thermistors for thermographic detection is known. This arrangement suggests using a plurality of thermistors, but does not describe an optimal arrangement or array of thermistors for breast cancer detection nor an optimal method for using the apparatus for breast cancer detection.